Silver recovery unit

ABSTRACT

An improved unit for the recovery of silver from spent photograhic processing solutions by a metallic replacement technique. The unit is designed to pass silver-bearing photographic processing solution through a roll of steel wool, and includes a high-density polyethylene cartridge to hold the steel wool, fitted with suitable plumbing for passing the solution through the roll in the cartridge. The polyethylene cartridge is essentially a drum with a generally flat lid, and includes a rim clamp for locking the lid tightly on the drum. The rim clamp fits around the top of the drum and has a lever lock operable from one side of the drum. The plumbing attached to a drum includes fittings for routing the solution into and out of the drum through a pair of openings in the cartridge lid. When the unit is in operation, feed solution passes into the top of the cartridge, contacts the steel wool roll in the cartridge drum, and then passes out of the drum for recycle use or discard to a sewer. The unit operates efficiently until the steel wool in the cartridge is exhausted, at which point it becomes necessary to replace the cartridge. This requires removal of the cartridge lid, but the removal can be easily accomplished without disconnecting the plumbing from the lid since the lever lock is operable from the side of the drum to permit loosening of the clamp for easy movement of the lid with the plumbing attached.

United States Patent 11 1 Larson et al.

[ SILVER RECOVERY UNIT [76] Inventors: Kay R. Larson, 1550 Columbia Ave., Pomona, Calif. 91766; John Drew, 54l-40th St., Richmond, Calif. 94805; Howard Ott, 124 Old Mill Rd., Great Neck, N.Y. 11023 22 Filed: Dec. 11, 1972 21 Appl. No.: 313,682

Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-John H. Crowe [57] ABSTRACT An improved unit for the recovery of silver from spent photograhic processing solutions by a metallic replacement technique. The unit is designed to pass sil- [45 Feb. 19, 1974 ver-bearing photographic processing solution through a roll of steel wool, and includes a high-density polyethylene cartridge to hold the steel wool, fitted with suitable plumbing for passing the solution through the roll in the cartridge. The polyethylene cartridge is essentially a drum with a generally flat lid, and includes a rim clamp for locking the lid tightly on the drum. The rim clamp fits around the top of the drum and has a lever lock operable from one side of the drum. The plumbing attached to a drum includes fittings for routing the solution into and out of the drum through a pair of openings in the cartridge lid. When the unit is in operation, feed solution passes into the top of the cartridge, contacts the steel wool roll in the cartridge drum, and then passes out of the drum for recycle use or discard to a sewer. The unit operates efficiently until the steel wool in the cartridge is exhausted, at which point it becomes necessary to replace the cartridge. This requires removal of the cartridge lid, but the removal can be easily accomplished without disconnecting the plumbing from the lid since the lever lock is operable from the side of the drum to permit loosening of the clamp for easy movement of the lid with the plumbing attached.

13 Claims, 6 Drawing Figures PAIENTEB FEB! 9 I974 SHEEI 2 OF 2 FIG. 5.

1 SILVER RECOVERY UNIT BACKGROUND OF THE INVENTION This invention relates generally to gravity flow apparatus for use in the recovery of silver from spent photographic processing solutions by a metallic replacement method, and more particularly to an improved form of such apparatus easier and more convenient to use, more corrosion resistant, and of lighter weight, than any previously existing apparatus of similar purpose of which we are aware.

Fairly recently, a commercial unit for the recovery of silver from spent sphotographic processing solutions became available on the market. This unit was designed to convert silver ions in the photographic processing solutions to metallic silver by a metallic replacement technique employing steel wool as a reducing agent. The unit comprises a stainless steel drum adapted to snugly receive a roll or pack of steel wool; a lid for the drum; a rim clamp having a metal band which can be tightened around the top edge of the drum to seal it or expanded to permit removal of the lid from the drum;

and plumbing designed to route the spent solution from a photographic processor into the top of the drum, and drain the desilvered solution from the drum for recycle in a bleach-fix regeneration system, or other disposition such as to a sewer or disposal sump. A spacer is provided to support the steel wool roll (a narrow layer of steel wool wound around a hollow cardboard core) above the bottom of the drum so as to leave space below the steel wool for the accumulation of a silverbearing sludge which forms in the drum as the solution circulates therethrough. The steel wool roll (sometimes hereinafter referred to as a filler) is, as previously indicated, positioned in the drum during this circulation of the solution through the silver recovery unit. The above-mentioned plumbing includes an input fitting, an output fitting, and an outlet tube, the input and output fittings being provided with coupling nuts to permit their threaded engagement with a pair of adaptors screwed into two tapped openings in the drum lid. One of these openings is at the center of the lid, and the outlet tube is permanently affixed to the lid so as to extend downwardly from this opening and into the hollow cardboard core of the steel wool filler(the outlet tube being sized to fit snugly within the core opening) when the lid is positioned on the drum.

I The aforesaid rim clamp is of the type having a curved lever arm movable between locked and unlocked positions of the clamp in a sweeping are through a plane closely parallel to the top of the drum lid. The sweep of this lever arm is of sufficient magnitude'to require the removal of the plumbing fixtures connected to the top of said lid before th e'rim clamp can be unlocked to permit removal of the lid from the drum. It is thus necessary to disconnect the plumbing from'the drum lid when it is time to change drums after exhaustion of the filler in the drum (see below).

Continued usage of the above-described prior art silver recovery unit results in consumption of the steel wool filler until the available iron in the filler is depleted to the point where little or no metallic replacement action can take place, at which time the unit cartridge (drum with steel wool filler) is said to be exhausted. When such a cartridge becomes exhausted, a new cartridge can be substituted therefor, or the car- 2 tridge drum can be reloaded with a new filler. In either event, however, it is necessary to disconnect the plumbing from the cartridge drum in order to unlock the rim clamp and remove the lid from the drum. Disconnection of the plumbing from the cartridge is tedious and time-consuming, and its periodic necessity constitutes an inherent disadvantage of the subject prior art unit. Additionally, the stainless steel construction of the cartridge drum and lid adds greatly to the weight of the unit, making it rather awkward and difficult to handle and move. To give some idea of the magnitude of this weight, a standard l5-gallon stainless steel cartridge of the type under consideration weighs approximately pounds when loaded with its steel wool filler. When this cartridge has been used to exhaustion, it'weighs approximately 220 pounds with a full load of solution. As will be apparent, the rather heavy weight of the stainless steel unit, preferably when loaded with solution, is a serious drawback to most effective handling and use thereof. Finally, while stainless steel offers substantial resistance to the corrosive ac-.

tion of spent photographic processing solutions, it is not totally immune to the attack of these solutions, and exhibits a small amountof rust when constantly exposed thereto. While the amount of this rust is small, it is sufficient to cause rust rings on floor surfaces and other rust deposits of unsightly character.

SUMMARY OF THE INVENTION We have now, by means of the present invention, provided a silver recovery unit of similar character and manner of functioning to the prior art unit described above, but differing from the latter in certain design improvements which permit handling and use of the apparatus without the above-described disadvantages and shortcomings.

Our silver recovery unit differs primarily from its above-mentioned prior art counterpart in having a rim clamp, preferably of the lever-lock variety, provided with a tightening and locking mechanism operable from one side, in place of the prior art rim clamp with its sweeping lever arm mounted to closely traverse the area adjacent the upper surface of the drum lid and conflict with the plumbing attached to said lid. The cartridge of our improved silver recovery unit is made from suitably hard, tough plastic material, preferably rotationally molded high-density polyethylene, to impart heavy duty use, and lightweight handling, properties thereto. By using such plastic material in place of stainless steel, we not only achieve the light weight handling and use advantages referred to above, but eliminate the chemical rust problems (rust rings on floors, etc.) resulting from the exposure of stainless steel cartridges to corrosive photograhic processing solutions.

It is thus a principal objectof this invention to provide apparatus for the recovery of silver from spent photographic processing solutions including a drum for holding a steel wool filler; a lid for the drum, plumbing means for routing spent photographic solutions into the drum for intimate contact with the steel wool and drainage of the solution from the drum after it has passed through the steel wool; and rim clamp means for fastening the lid tightly to the drum having locking means operable to permit loosening and removal of said lid without disconnection of any plumbing attached thereto.

It is another object of the invention to provide such silver recovery apparatus of relatively light weight drum and lid construction which can be handled and used with relative ease.

It is still another object of the invention to provide such apparatus which is resistive to rust when exposed to spent photographic processing solutions so as to leave no rust rings on floors, or exhibit other unsightly manifestations of the presence of rust, in use.

Other objects, features and advantages of the invention will become apparent in the light of subsequent disclosures herein.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a preferred form of sil- ,ver recovery cartridge with attached plumbing in accordance with this invention, a portion of the cartridge wall being broken away and part of a steel wool filler being shown in section in the cartridge.

FIG. 2 is an enlarged vertical section of the cartridge and attached plumbing minus said steel wool filler;

FIG. 3 is an enlarged view of that portion of the silver recovery apparatus encircled by the loop with the arrowhead in FIG. 2.

FIG. 4 is a perspective view, somewhat similar to FIG. 1, of a modified form of silver recovery cartridge with attached plumbing, and loaded with a steel wool filler, in accordance with this invention. 7 FIG. 5 is an enlarged vertical section of the FIG. 4 cartridge and attached plumbing, minus the steel wool filler.

FIG. 6 is a still further enlarged view of that portion of the apparatus encircled by the loop with the arrowhead in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Considering now the drawing in greater detail, there is shown generally at 10 a preferredembodiment of a silver recovery unit in accordance with this invention. FIG. 1 shows the unit complete with steel wool pack or filler 12, having a hollow cardboard core 13, positioned for use therein, and FIG. 2 is a sectional view of the unit without the steel wool filler. The silver recovery unit 10 consists of a, cartridge 16' and accessory plumbing and other components as will be described below. The cartridge 16 comprises a plastic drum 18 with a plastic lid 20 and a rim clamp 22 for locking the lid to the drum i in fluid-tight relationship. The lid is provided with a resilient O-ring gasket to assure a tight seal between the lid and the drum when rim clamp 22 is in its locked position. The O-ring gasket must, of course, be made from a suitably resilient material substantially impervious' to attack by the solutions passing through unit 10 when the latter is'in use. We have found Buna-N, pref.- erably of SO-Shore hardness, to be a suitable material for this purpose, Buna-N being a synthetic rubber produced by the copolymerization of butadiene and acrylonitrile. Although the above-mentioned prior art silver recovery unit with the stainlesssteel drum and lid has a sealing gasket of similar shape to gasket 15, that gasket is not, to our knowledge, made from Buna-N, and does not affect as permanent or complete a seal for the unit cartridge as does our Buna-N gasket.

Drum 18 and lid of cartridge 16 are made from a tough, relatively light weight plastic of a type substantially impervious to attack by the photographic processing solutions to which unit 10 will be exposed in service. Preferably, the drum and lid are of rotationally molded, high-density polyethylene, prepared by techniques, and using reactants and other ingredients well known to those skilled inthe resin and plastic arts. Drum 18 has a pair of diametrically opposed handles 42, molded into its side walls. These handles, coupled with the light weight of the drum, facilitate easy movement and handling of the latter. The drum is preferably of l5-gallon capacity, a size particularly suitable for use in the recovery of silver from bleach-fix solutions in bleach-fix regeneration systems. Although we do not wish to be so limited, we have found a wall thickness of one-fourth inch satisfactory for heavy-duty use of our plastic cartridge drums.

Drum 18 has an outwardly flaring rim 30 around its top, and lid 20 has an annularly upstanding peripheral flange 32- which merges into a beaded lip 34 of arcuate cross section designed to overlie the flaring rim of drum 18 when the lid is placed on the drum. Gasket 15 is sized'to fit around the outer side of the-peripheral flange 32, and nest in the curved undersurface of lip 34, so that it will be in sealing position around the top of the cartridge when the lid is tightened on the drum with rim clamp22 in the hereinafter-described manner.

Rim clamp 22 is of the familiar type consisting of a metal band of C-shaped cross section with a lever lock 24 attached in such a way as to be operable at the outer side of the band for use during expansion or contraction of the latter. As will be clear from the drawing, lever lock 24 is acommon typeof locking mechanism for rim clamps of this type, which are employed in large numbers'on fiber drums and similar containers. For a more detailed description of this type of lever lock, see US. Pat. No. 2,579,975 to Scott et al. As will be apparent, lid 20 can be secured to drum 18 by tightening rim clamp 22 around the top of the drum and locking it in the position shown in FIG. 1. As will also be apparent, the rim clamp can be loosened from its tightened position, to permit removal of the lid from the drum, solely through the manipulation of lever lock 24, and without disturbance of any of the below-described plumbing attached to the lid. This is an important feature of our invention. and permits interchange of the lids and drums of our cartridge units without any prior disengagement of such plumbing. This kind of interchange, absent precedent plumbing disengagement is not possible with the prior art stainless steel units described above.

Lid 20 has two openings defined by downthrust, internally threaded sockets, one socket being situated at the center of the lid, as shown at 38, and the other between the center and the edge of the lid, as shown in FIG. 2 at-40. These sockets 38 and 40 serve to receive a pair of adaptors, subsequently to be described, for the accommodation of a circulating unit 44, also subsequently to be described.

Circulating unit 44 is equivalent, or substantially similar, to a product manufactured and sold by Eastman Kodak Company, as KODAK Circulating Unit, Type P, for use in conjunction with a line of silver recovery cartridges also manufactured and sold by Kodak. The circulating unit has a T-shaped inlet fitting 46, a similarlysized and T-shaped outlet fitting 52, and a U-shaped length of transparent industrial hose S8 connecting a pair of upstanding tubular segments of the inlet and outlet fittings, all as illustrated in the drawings. Captive between annular shoulders around the lower ends of each of the inlet and outlet fittings are a pair of coupling nuts 56. Nuts 56 permit attachment of the inlet and outlet fittings to the aforesaid adaptors, which latter are screwed into the openings in sockets 38 and 40 i in lid 20 of the assembled unit 10. The manner of assembly of the unit will be clear from FIGS. 2 and 3, which show, inter alia, the aforesaid adaptors in sockets 38 and 40 at 62 and 64, respectively. Adaptor 62 is threaded internally from the bottom, for a portion of its length, to receive an outlet tube 66 in the manner best illustrated in FIG. 3, the latter being fixedly secured in threaded engagement with the adaptor by means of a suitable epoxy or other cement. To make this possible, the outlet tube 66 has an externally threaded sleeve 72 fixedly secured to its upper end with a cement such as that used to secure the outlet tube to the adaptor 62. The inlet and outlet fittings of circulating units 44 (including coupling nuts 56), adaptors 62 and 64 and outlet tube 66 are all made ofa plastic material, or materials, suitably resistant to attack by the photographic processing solutions to which they will be exposed in use. Polyvinyl chloride (PVC) plastic is, we have found, a preferred material for this purpose.

In addition to cartridge l6.and the circulating unit, and other, plumbing components described above, unit includes, as an accessory part, a bottom spacer 26. Bottom spacer 26 is a round plastic plate, preferably of PVC construction (although it can be of any other material suitable for the purpose) having a round opening in it center and a plurality of equally sized bubble protrusions 28 extending upwardly and downwardly therefrom in spaced-apart relationship, all as illustrated in the drawing. Bottom spacer 26 is positioned for use in the bottom of drum 18 so that the protrusion on its underside serve as support feet therefor, whle their upwardly extending counterparts provide a base for the bottom of the steel wool filler or pack 12 to rest on, as will be explained. As will perhaps now be evident, bottom spacer 26 serves to support the steel wool filler at a suitable level above the bottom of drum 18 to leave space for the accumulation of a silver-bearing sludge which forms continuously in unit 10 during operation of the latter, similarly to the way in which such a sludge forms in the stainless steel prior art unit of above reference. v

In assembling unit 10 for use, care should be taken to see that bottom spacer 26 is properly positioned in drum 18. The steel wool filler 12 should then be pushed downwardly within the drum until it rests on the upwardly extending protrusions 28 of the bottom spacer. This filler is sized to fit snugly within the drum so as to occupy all of the cross-sectional space therewithin except for the hollow in its cardboard core 13. When filler 12 is positioned for use in the drum, core 13 is disposed directly underneath the opening of socket 38 in lid when the latter is placed on the drum. The above-described plumbing fixtures are attached to lid 20 for use by first screwing the adaptors 62 and 64, fitted with a pair of resilient O-ring seals 68, into the threaded openings of sockets 38 and 40 in said lid. Adaptor 62, as explained above, has outlet tube 66 so affixed as to extent concentrically downwardly therefrom, as seen in FIGS. 2 and 3, and into the hollow center of the steel wool core 13, when lid 20 is placed on drum 18. The inlet and outlet fittings of circulating unit 44 are attached to the upper ends of adaptors 64 and 62 by screwing their captive coupling nuts downwardly onto external threads on the adaptors, as best illustrated in FIG. 3 which shows the outlet fitting 52 so attached to adaptor 62. A pair of washers are provided to form a seal between the adaptors and circulating unit fittings.

Lid 20, with its plumbing accessories attached, can easily be positioned on, or removed from, drum 18 if care is taken to insure alignment between outlet tube 66 and the hollow center of the steel wool filler core so that the tube slides freely within the core. While the outlet tube must be small enough in diameter to slide easily within core 13, its fit within this core must be snug enough to substantially prevent the channeling of solution downwardly through the latter since such channeling would deleteriously affect the operation efficiency of the silver recovery unit. After lid 20 is positioned on drum 18, as described, it is fastened in place by placing the expanded rim clamp 22 therearound and tightening and locking the latter through manipulation of lever lock 24.

We have made and commercially tested a number of silver recovery units structurally similar to unit 10. These units were found to be fluid-tight to pressures of 5 psig and outstandingly successful in operation. To place a unit of this type (hereinafter discussed in terms of reference to unit 10) in service, it is necessary only to connect a feed hose, of the type presently employed as a feed line for the Eastman Kodak unit referred to below from a photographic processor to the inlet fitting of its circulating unit 44 (by attaching the hose to a tubular connection 48 on the inlet fitting), and a recycle, or drain, hose (of similar character to the feed hose) to the outlet fitting of the circulating unit (by attaching the hose to a tubular connection 54 on the outlet fitting). The unit is now ready. for operation, during which spent photographic processing solution passes by gravity flow through drum 18 until the steel wool filler therein is exhausted. Sludge accumulates in the bottom of the drum while the unit is in operation, from whence it (the sludge) can later be removed for assay and silver recovery treatment. An opening 60 in the curved top portion of the by-pass line 58 of curculating unit 44 serves as an air vent. The way in which unit 10 is installed in a photographic processing system for use is similar to the way in which the above-mentioned prior art Kodak unit is installed, hence need be considered in no greater detail here.

As previously made clear, the unique silver recovery unit of our invention is in the nature of an improvementon a prior. art unit of generally similar purpose and function. As also made clear, our novel unit differs from its prior art predecessor in features contributive to simplified and Y relatively low cost manufacturing techniques, easy and efficient use and functioning of the unit, rust-free operation of the unit, etc., yet is essentially equivalent to the latter insofar as sizes of common plumbing components,'manner of hookup in a photographic processing system, etc., are concerned. In this connection, unit 10, in its l5-gallon drum form referred to above, is sufficiently similar to the abovedescribed stainless steel unit of l5-gallon drum capacity (its prior art predecessor") to permit the free interchange of parts (other than those which critically distinguish the two units) therebetween. More specifically, and as previously pointed out, essentially the asme type of circulating unit will suffice for use in either of these silver recovery units. The stainless steel cartridge of the lS-gallon prior art unit is manufactured and sold by Eastman Kodak Company under the name KODAK Chemical Recovery Cartridge, Type 3. Kodak also sells the necessary steel wool roll or filler for use in its Type 3 cartridge, as Kodak Cartridge Refills, Type 3. These refills are formed from relatively coarse metallic, fibers, and each contains 24 lbs. of steel wool wound on its core. While the Kodak filler is suitable for use in the l-gallon cartridge of our invention, any other steel wool filler of similar size and type can, if desired, be employed in lieu thereof (including fillers formed from fine, rather than coarse, metallic fibers,

which are preferably for use with certain types of photographic processing solutions). In this connection, a commercially available'filler from a source other than Kodak which we have found particularly suitable for our purpose is made and sold by James H. Rhodes & Company, of Chicago, as Beaver Brand Steel Wool.

Silver-bearing photographic processing solution passes through the silver recovery unit of our invention similarly to the way it passes through the Kodak Type 3 unit. In each case, the feed solution enters the cartridge at the top, through its lid, to fill the cartridge drum and immerse the steel wool filler therein, then flows out of the cartridge through outlet tube 66, or its counterpart in the Kodak unit. There must be a space in the cartridge drum between the top of the steel wool filler and the cartridge lidfor most effective feeding of the solution to the cartridge. This is provided for in the Kodak Type 3 cartridge by means of a pair of wooden spacers which fit into the top of the cartridge to hold the steel wool filler preperly spaced from the cartridge lid. In our silver recovery unit no such spacers are necessary, since the downturned socket (38) defining the center opening in the cartridge lid serves the same purpose by bearing on the upper end of the cardboard core of steel wool filler 12. For this reason, downturned socket 38 is made longer than socket 40, as can be seen in FIG. 2. Preferably the downward extension of socket 3.8 from the bottom of the cartridge lid is slightly in excess of 1 /2 inches, and of socket 40, slightly in excess of 1 inch. This design contributes to still further improvement of our unit 10 over its stainless steel prior art counterpart in that it eliminates the need for top spacers in the unit cartridge with attendant cost, convenience of use and feed solution flow advantages.

The Kodak Type 3 stainless steel cartridge is nromally shipped with plugs'in the solution inlet and outlet openings in its lid. Our unit, on the other hand, can be shipped with adaptors 62 and 64 screwed into the lid openings, and cap closures (not shown in the drawing) screwed onto the adaptors. This mode of shipment is possible because our cartridge lid can be put on or taken off of the cartridge by operating its rim clamp locking mechanism fromthe side, since-this mechanism has no lever arm, or the like, movable in a path which would be blocked by the upstanding adaptors. This is not true of the stainless steel prior art cartridge, however, since the presence of such adaptors there would prevent the swinging lever arm movement necessary for opening and closing of the rim clamp 'of that cartridge.

The description of this point has centered around the silver recovery unit illustrated in FIGS. 1 thorugh 3 at 10. FIG. 4 shows, at 72, another form of our silver recovery unit. Silver recovery unit 72 is quite similar to unit 1-0 in many aspects, having a cartridge comprising a plastic drum with a plastic lid and a rim flange, and including a circulating unit for use in running solution to be treated through the unit. Unit 72 differs primarily from unit 10 in the shape of its lid (shown at 74 in FIGS. 4, 5 and 6). In order to highlight the points of dif ference between silver recovery units 72 and 10, like parts of the two units will be here designated by their unit 10 reference numerals, whereas all components and/or features of unit 72 without like counterparts in unit 10 will be referred to by new reference numerals.

As indicated above, the lid 74 of silver recovery unit 72 differs from the lid of unit 10. The difference between these lids can best be seen in FIG. 5. Lid 74 fits, and is fastened to drum 18 of the unit cartridge similarly to the way lid 20 of the unit 10 cartridge fits and is fastened to drum 18 of unit 10. Also, similarly to lid 20, lid 74 has two openings positioned for the accommodation of a circulating unit 44. The openings in lid 74, however, are defined by a pair of upthrust, externally threaded bosses 76 and 78, respectively, rather than the downthrust internally threaded sockets of lid 20. As the drawings illustrate, bosses 76 and 78 are adapted to directly receive the coupling nuts 56 of the inlet and outlet fittings of circulating unit 44 in threaded engagement. Thus, as will be apparent, it is unnecessary, with lid- 74, to use adaptors on the lid openings for the accommodation of the circulating unit. This, of course, results in simplification and cost reduction in the manufacture and use of the silver recovery unit.

As FIG. 6 best shows, the center opening boss (76) on lid 74 is internally threaded part of the way up from the bottom. The purpose of this is to permit the lid to receive, in threaded engagement, an outlet tube 80. OUtlet tube 80 is somewhat similar to outlet tube 66 of silver recovery unit 10, except that it has no externally threaded sleeve around its upper end, as. does outlet tube 66, but is, instead, threaded at its upper end for engagement with the internally threaded socket of boss 76, as illustrated at 86 in FIG. 6'. As FIGS. 5 and 6 make clear, the threads on bosses 76 and 78 of lid 74, on the coupling nuts of circulating unit 44, and on outlet tube 80 are all tapered to be self-sealing when the resulting fittings are tightened. The internally threaded portion of center boss 76 terminates at a shoulder 84, against which the upper end of outlet tube 80 abuts when that tube is screwed as far as it will go into this portion of the center boss, as illustrated in FIG. 6. .This simplified manner of fastening the outlet tube in position contributes to still further simplicity of manufacture and use of silver recovery unit 72, as compared to unit 10. Unit 72 does, however, require the use of spacers (not shown) above filler 12, to hold the latter in place during operation of the unit, since it has no downthrust socket to perform that function as does socket 38 in the unit 10 lid. The spacers can be of the same type as those employed-in the Kodak Type 3 cartridge.

Because of its unique design and construction, our silver recovery unit is the lowest cost metallic recovery system commercially available, at least insofar as we are aware. Our plastic'cartridge is capable of heavyduty use for a virtually indefinite period. The cartridge can be kept in continuous use by merely replacing its metallic fillers as the fillers becomes exhausted. The replacing of only the metallic fillers results in much lower in-plant recovery costs per ounce of silver than is possible where whole cartridge drums are replaced. Sludge shipping costs are minimal where the photographic processor uses a filler recharging procedure, since the sludge can be accumulated for shipment to a sludge processor in special containers for large batches, rather than being shipped in exhausted cartridges. Moreover, our -gallon silver recovery unit is 30 pounds lighter than its stainless steel prior art counterpart, which contributes to further shipping cost reduction, as well as to greater handling convenience.

For the foregoing reasons, and other apparent to those skilled in the art, our novel silver recovery unit has ease-of-handling features which significantly reduce the down-time of' the unit in metallic recovery systems and result in cleaner, neater handling thereof.-

While the drums and lids of our novel units are interchangeable with the drums-and lids of their presently known prior art stainless steel counterparts of similar capacity, this is only a preferred, an not a limiting feature of our invention.

Although the term cartridge has been employed herein in terms of referenced to the drum, lid and rim clamp of our silver recovery unit on the one hand, and

the drum, lid and rim clamp of the prior art stainless steel unit complete with a steel wool filler, on the other hand, no confusion should result from this language because of the clear line of distinction drawn between these two units in the present disclosure. Since the openings in the lid of our novel silver recovery unit can be defined by either the downthrust sockets of unit 10 or the upthurst bosses of unit 72, these opening defining lid protuberances will be genericallyreferred to in the claims to follow as outthrust bosses.

While the novel silver recovery unit of our invention has been herein illustrated and described in what are considered to be their preferred embodiments, there are, as will be appreciated, many variations of these embodiments within the scope of the invention. Certain of these variations have already been mentioned and others will occur to those skilled in the art in the light of present teachings. Examples ofthe latter result when noncritical changes are made in the shapes of various parts, or features, of the illustrated unit; equivalent materials of construction are substituted for the preferred materials mentioned above; certain structural, or other, features of the unit not critically essential to its proper use and functioning are eliminated; useful, but noncritical, hardware, or other, means are incorporated in the illustrated unit; etc. I

While this disclosure has emphasized the use of our novel unit for the recovery of silver from spent photographic processing solutions, it should be understood that the unit is not necessarily limited to this use potential and can be employed in any capacity for which its unique character fits it.

We Claim:

1. Cartridge means particularly suitable for use in the a rim clamp adapted to encircle and radially embrace the edges of the outturnedflange of the drum and the overlying peripheral lip of said lid, when the lid is positioned on said drum, said rim clamp being of an expansible and contractible type whereby it can be tightened and locked to fasten the lid in place on the drum, and having a locking mechanism operable at the outer periphery of the clamp to permit the latter to be loosened, for removal of the lid from the drum, without the necessity of separating said plumbing means from said lid.

2. Cartridge means in accordance with claim 1 in which the desilvering treatment comprises subjecting the feed solution to intimate contact with steel wool wound in the form of a roll around a hollow core and snugly positioned in said drum, and said cartridge means includes a spacer means adapted to support the steel wool roll at a level above the bottom of the drum to provide space in the bottom of said drum for the ac cumulation of the below-mentioned sludge;

whereby silver is precipitated from said solution as a result of metallic replacement action when the silver contacts said steel wool, and the precipitated silver gravitates to said space in the bottom of said drum as a component of a sludge which can be removed for recovery of said silver.

3. Cartridge means in accordance with claim 2 in which said locking mechanism is a lever lock.

4. Cartridge means in accordance with claim 3 in which said drum and lid are each made of a heavy duty plastic material substantially impervious to attack by said feed solution.

5. Cartridge means in accordance with claim 4 in which the drum and lid are of rotationally molded, high-density polyethylene construction.

6. Cartridge means in accordance with claim 5 including an O-ring gasket for said lid, said gasket being made of a rubbery material substantially impervious to attack by said feed solution and capable of providing a tight seal around the top of said drum when said lid is fastened in place thereon by means of said rim clamp.

7. Cartridge means in accordance with claim 6 in which said gasket is made of Buna-N rubber.

8. Cartridge means in accordance with claim 7 in which said pair of downthrust sockets defining openings in said lid includes a first socket situated at the center of the lid, said tubular core of said steel wool roll is positioned directly underneath said first socket when said drum is loaded with said roll for operation of said cartridge means, and the bottom of said first socket is aligned with said tubular core and serves as a stop to prevent upward'movement of the latter to thereby hold said steel wool roll at the proper level within said drum to provide space thereabove for the inflow of feed solution during operation of saidcartridge means.

9. Cartridge means in accordance with claim 7 in which said pair of outthrust bosses defining openings in said lid comprise a pair of upthrust, externally threaded bosses of round cross section, including a first boss situated at the center of the lid and said tubular core of said steel Wool roll is positioned directly underneath said first boss when said drum is loaded with said roll for operation of said cartridge means.

10. Cartridge means in accordance with claim 8 in combination with an outlet tube forming part of said plumbing means and adapted to extend downwardly from said first socket in said lid and fit snugly within said tubular core, when the lid is positioned on the drum, to receive desilvered solution which has passed through said steel wool to permit drainage thereof from said drum during operation of the cartridge means.

11. Cartridge means in accordance with claim 9 in combination with an outlet tube forming part of said plumbing means and adapted to extend downwardly from said first boss in said lid and fit snugly within said tubular core, when the lid is positioned on the drum, to receive desilvered solution which has passed through said steel wool roll to permit drainage thereof from said drum during operation of the cartridge means.

12. The cartridge means-outlet tube combination of claim 11 in which said plumbing means includes a circulating unit having a T-shaped inlet fitting with a first tubular vent adapted to route feed solution from a feed line into said drum when the cartridge means is in service, a T-shaped outlet fitting with a second tubular I vent adapted to route desilvered solution from said outlet tube into a drain line from said drum when said cartridge means is in service, and a U-shaped by-pass tube with a vent opening in the top of its bight connecting the first and second tubular vents in the inlet and outlet fittings; the inlet and outlet fittings being adapted for threaded connection with said externally threaded bosses, said first boss being threaded internally from the bottom and said outlet tube being externally threaded at its upper end whereby said outlet tube is threadedly engageable with said first boss for downward extension therefromvwithin said tubular core.

13. The combination of claim 12 in further combination with said steel wool roll.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,792,845 DATED February 19, 197

INVENTOR(S) Kay R. Larson, John Drew and Howard Ott It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Abstract, line 13, "a" should read -the- Column 2, line 18 "preferably" should read -particularly- Column 5, line 17, "units" should read --unit-- line 34, "protrusion" should read -protrusionsand, line 62, "extent" should read -extend- Column 6, line 66, "asme" should read -same Column 7, line 13, "preferably" should read -pref'erable- Column 8, line 35, "OUtlet" should read -Outlet Column 9, line 10, "other" should read --others-- and, line 21, "referenced" should read --reference Column 10, line 17, cancel "a" Bigncd and Scaled this Twenty-third D f M y I [SEAL] A no":

RUTH MASON LUTRELLE F. PARKER Arresting ()jlicer Acting Commissioner of Parents and Trademarks 

1. Cartridge means particularly suitable for use in the recovery of silver from spent photographic processing solutions comprising, in combination: a drum with an outturned flange around its top; a lid for said drum having a peripheral lip adapted to fit over said outturned flange, said lid being further characterized by the presence of a pair of outthurst bosses defining openings therethrough, the outthrust bosses being adapted to receive plumbing means for admitting feed solution to said drum for desilvering treatment therein and draining the solution from the drum after it has been desilvered; and a rim clamp adapted to encircle and radially embrace the edges of the outturned flange of the drum and the overlying peripheral lip of said lid, when the lid is positioned on said drum, said rim clamp being of an expansible and contractible type whereby it can be tightened and locked to fasten the lid in place on the drum, and having a locking mechanism operable at the outer periphery of the clamp to permit the latter to be loosened, for removal of the lid from the drum, without the necessity of separating said plumbing means from said lid.
 2. Cartridge means in accordance with claim 1 in which the desilvering treatment comprises subjecting the feed solution to intimate contact with steel wool wound in the form of a roll around a hollow core and snugly positioned in said drum, and said cartridge means includes spacer means adapted to support the steel wool roll at a level above the bottom of the drum to provide space in the bottom of said drum for the accumulation of the below-mentioned sludge; whereby silver is precipitated from said solution as a result of metallic replacement action when the silver contacts said steel wool, and the precipitated silver gravitates to said space in the bottom of said drum as a component of a sludge which can be removed for recovery of said silver.
 3. Cartridge means in accordance with claim 2 in which said locking mechanism is a lever lock.
 4. Cartridge means in accordance with claim 3 in which said drum and lid are each made of a heavy duty plastic material substantially impervious to attack by said feed solution.
 5. Cartridge means in accordance with claim 4 in which the drum and lid are of rotationally molded, high-density polyethylene construction.
 6. Cartridge means in accordance with claim 5 including an O-ring gasket for said lid, said gasket being made of a rubbery material substantially impervious to attack by said feed solution and capable of providing a tight seal around the top of said drum when said lid is fastened in place thereon by means of said rim clamp.
 7. Cartridge means in accordance with claim 6 in which said gasket is made of Buna-N rubber.
 8. Cartridge means in accordance with claim 7 in which said pair of downthrust sockets defining openings in said lid includes a first socket situated at the center of the lid, said tubular core of said steel wool roll is pOsitioned directly underneath said first socket when said drum is loaded with said roll for operation of said cartridge means, and the bottom of said first socket is aligned with said tubular core and serves as a stop to prevent upward movement of the latter to thereby hold said steel wool roll at the proper level within said drum to provide space thereabove for the inflow of feed solution during operation of said cartridge means.
 9. Cartridge means in accordance with claim 7 in which said pair of outthrust bosses defining openings in said lid comprise a pair of upthrust, externally threaded bosses of round cross section, including a first boss situated at the center of the lid and said tubular core of said steel wool roll is positioned directly underneath said first boss when said drum is loaded with said roll for operation of said cartridge means.
 10. Cartridge means in accordance with claim 8 in combination with an outlet tube forming part of said plumbing means and adapted to extend downwardly from said first socket in said lid and fit snugly within said tubular core, when the lid is positioned on the drum, to receive desilvered solution which has passed through said steel wool to permit drainage thereof from said drum during operation of the cartridge means.
 11. Cartridge means in accordance with claim 9 in combination with an outlet tube forming part of said plumbing means and adapted to extend downwardly from said first boss in said lid and fit snugly within said tubular core, when the lid is positioned on the drum, to receive desilvered solution which has passed through said steel wool roll to permit drainage thereof from said drum during operation of the cartridge means.
 12. The cartridge means-outlet tube combination of claim 11 in which said plumbing means includes a circulating unit having a T-shaped inlet fitting with a first tubular vent adapted to route feed solution from a feed line into said drum when the cartridge means is in service, a T-shaped outlet fitting with a second tubular vent adapted to route desilvered solution from said outlet tube into a drain line from said drum when said cartridge means is in service, and a U-shaped by-pass tube with a vent opening in the top of its bight connecting the first and second tubular vents in the inlet and outlet fittings; the inlet and outlet fittings being adapted for threaded connection with said externally threaded bosses, said first boss being threaded internally from the bottom and said outlet tube being externally threaded at its upper end whereby said outlet tube is threadedly engageable with said first boss for downward extension therefrom within said tubular core.
 13. The combination of claim 12 in further combination with said steel wool roll. 